The United States Senate elections of 1884 and 1885 were elections that coincided with the presidential election of 1884. Both Republicans and Democrats lost seats in the United States Senate due to the failure of three state legislatures to finish elections in time. Republicans, nevertheless, retained majority control and the Readjusters joined their caucus. By the beginning of the first session, in December 1885, Republicans had won all three vacant seats, increasing their majority.

The caucus of Republican State legislators met on January 19, President pro tempore of the State Senate Dennis McCarthy presided. 19 State senators and 73 assemblymen attended. The Evarts faction required the nomination to be made by viva voce vote, which was opposed by the Morton faction, but was carried by a vote of 64 to 28. The caucus nominated Ex-U.S. Secretary of State William M. Evarts on the first ballot.

In 1884, the Democrats held a majority in the Ohio legislature. In a caucus meeting to determine the party's choice for United States Senator, many Democratic legislators looked to replace the incumbent Senator, Democrat George H. Pendleton, because they disagreed with his advocacy of civil service reform and low tariffs.[5] Some of Pendleton's opponents, led by Oliver Payne, promoted Henry B. Payne for the Senate seat, recalling his opposition to both of those positions during his time in the House.[6] After a secret ballot by the Democratic caucus, Henry B. Payne received 46 out of 80 votes.[7] Because Oliver was a trustee and treasurer of the Standard Oil company, many of the Pendleton supporters immediately alleged that $100,000 from the oil trust had been used to bribe Democratic legislators, and claimed that an open ballot would not have favored Payne.[8][9]

When the full legislature met, Henry B. Payne was elected with 78 votes out of 120.[7] The Democratic legislature initially refused to investigate their members' alleged corruption, but when Republicans regained the majority in the next session, the legislature looked into the allegations and forwarded the results to the federal Senate.[10] The evidence gathered was voluminous, but the Senate declined to expel Payne, who proclaimed his innocence.[9] While there was never enough evidence for definitive proof of bribery, biographer Dewayne Burke wrote that the "circumstantial evidence seems to convict Payne" of the charge.[11]

The Pennsylvania election was held January 20, 1885. The Pennsylvania General Assembly convened January 20, 1885. Incumbent RepublicanJ. Donald Cameron, who was elected in an 1877 special election and re-elected in 1879, was a successful candidate for re-election to another term.[12] The results of the vote of both houses combined are as follows: